The trouble with curved orders is that when the object projects to only one or two pixels on the detector, the bulk of the signal will sometimes fall into one pixel and sometimes it will be split between several pixels. This means that there is no single correct number of rows of data to extract, forcing the extraction of unwanted sky as well as wanted signal. It would be possible to provide some optimal extraction scheme that would make a sensible decision about how many rows of data to extract at each point along the order, but any such scheme needs accurate knowledge of the noise characteristics of the data. The FIGARO approach is to use CDIST to resample in the Y direction to straighten the orders, so the number of rows to extract for object and for sky is merely a function of order number and not also of wavelength.